The present invention relates to a composite aerofoil, in particular to a composite fan blade, for a gas turbine engine.
Conventionally compressor blades, or fan blades, comprise forged, or machined, solid metal.
One problem with conventional solid low-pressure compressor blades, or fan blades, is that they are relatively heavy in weight due to their size. The gas turbine engines to which these fan blades are secured require that the rotor disc is made sufficiently strong to carry the operational loads of the fan blades and this entails strengthening the rotor disc and as such means increasing the mass and weight of the rotor disc. In addition the gas turbine engines to which these fan blades are secured require that the fan casing containment system is sufficiently strong to contain a fan blade should it become detached due to bird ingestion and as such means increasing the mass and weight of the fan casing. Thus these features add to the weight of the gas turbine engine.
In order to reduce the weight of large compressor blades, e.g. low-pressure compressor blades or fan blades, it is known for the fan blade to comprise a number of metal workpieces, which are diffusion bonded together with an intervening honeycomb structure to produce a hollow fan blade. This reduces the weight of the fan blade and enables corresponding reductions in the weight in the rotor disc and fan casing containment system.
In order to reduce the weight of large compressor blades, e.g. low-pressure compressor blades or fan blades, it is known for the fan blade to comprise a number of metal workpieces, which are diffusion bonded together and superplastically formed to produce a hollow fan blade. This reduces the weight of the fan blade and enables corresponding reductions in the weight in the rotor disc and fan casing containment system.
Also in order to reduce the weight of small and large compressor blades, e.g. low-pressure compressor blades or fan blades, it is known for the fan blade to comprise a composite material, for example fibre, or cloth, reinforced resin. It is also known for the composite material fan blade to comprise metal parts. This also reduces the weight of the fan blade and enables corresponding reductions in weight in the rotor disc and fan casing containment system.
However, a low-pressure compressor blade, or fan blade, comprising composite material has substantially the same weight as a hollow low-pressure compressor blade, or hollow fan blade, comprising a number of metal workpieces, which are diffusion bonded together and superplastically formed.